1. Field of the Invention
This invention relates generally to the field of particle deposition on a material. More particularly, it relates to an apparatus for the deposition of nanoparticles onto a biological material.
2. Description of the Related Art
Nanomaterials (NMs) are generally defined as a material with a base constituent that is between 1×10−9 and 100×10−9 meters in length with at least one property that deviates from the equivalent bulk material. Nanotechnology is driven largely by the idea that the ability to manipulate NMs by advanced synthesis methods and surface modifications will lead to tailorable and enhanced properties. Continuous innovation in synthesis and characterization of NMs have led to a more advanced understanding of the relationship between nanostructure and properties, and the exploitation of properties inherent to materials at the nano-scale has resulted in rapid growth in the field of nanotechnology. For example, aluminum NMs have been used by the U.S. Army in solid rocket fuel and by the U.S. Naval Air Warfare Center to replace lead primers in artillery and wear-resistant coatings on propeller shafts.
Changes in physicochemical properties at the nano-scale are the basis of the unique nature and value of NMs. However, these properties are also cause for concern regarding the toxicological effects of NMs on biological systems. When inhaled, NMs are capable of depositing deep within the alveolar portion of the respiratory tract and may induce local inflammation and oxidative stress. NMs may also be introduced into the body via dermal contact and ingestion, and the ability of NMs to pass through cell membranes and tissues or be distributed throughout the lymphatic and circulatory systems could result in unintended hazardous consequences. Because NMs are smaller than eukaryotic cells and most organelles, they may be taken up within these structures, potentially interfering with cellular processes. In addition to size, additional properties of NMs that can cause interaction with cells include surface chemistry, surface charge, stability (e.g. ion dissolution), and purity. Chronic exposure to NMs in air pollution has been linked to a variety of diseases, including cardiovascular disease, asthma, and diabetes.
While there are advantages and drawbacks for both in vitro and in vivo NM toxicity studies, there is strong motivation to improve alternative techniques to reduce, replace, or refine the use of animals. Due to the costs and ethical issues associated with in vivo toxicity studies, it is critical to improve in vitro techniques for more rapid testing of toxicity of NMs, which include a diverse and rapidly expanding range of materials. Traditional in vitro assays require that NMs be dispersed in biological media and administered to cells, which can induce NM aggregation. These techniques may also alter the properties of NMs and do not mimic realistic inhalation exposure, often yielding contradictory and inconclusive results. Additionally, the dosimetry is very difficult to predict in NM dispersion, which is the often the most critical feature of toxicity investigations. When NMs are exposed to the lung via inhalation, they are deposited in the gas phase onto cell layers covered in a thin layer of mucus, making in vitro studies at the air-liquid interface an appropriate mechanism for investigating the inhalation toxicity of NMs.
Major challenges associated with building a system for exposing at the air-liquid interface include controlled particle generation, predictable and uniform particle deposition, and controlled cellular environment (100% humidity, 37° C.). A complete system must generally include strategically placed conductive components for electrostatic deposition of NMs, adjustable inlet tube heights, in addition to well-designed heating and humidity generation/monitoring. Previous attempts to study NM toxicity at the air-liquid interface have run into a number of problems, including particle agglomeration and uneven particle distribution and dosing.